Auxiliary Modes

The auxiliary modes refer to those tasks that are carried out in preparation for other observing modes and that are needed to ensure the quality of the MEGARA observations. In general, these observing modes are not useful per se, neither for straight scientific exploitation nor even data-processing purposes.

These Auxiliary modes are intended to (1) allow the observatory staff to prepare the instrument for its optimal exploitation or (2) to improve the performance of the telescope procedures in terms of the target acquisition and focus.

With regard to the former, the following modes are defined:

• Telescope focus

• Spectrograph focus

These observing modes might have to be run before any observing run (in case of visitor mode observations) and certainly after a long period of inactivity of the instrument. Below we provide a detailed description of each of these observing modes. Regarding the auxiliary observing modes defined to improve the default telescope procedures these are:

• (The two previous observing modes)

• Fine acquisition with the LCB IFU

• Fine acquisition with the Fiber MOS

These latter three observing modes should be run before any observing run (in case of visitor mode observations) and after a long period of inactivity of the instrument; at least in the instrument mode to be used (LCB or MOS).

Telescope focus

Mode:

Telescope Focus

Usage:

Online

Key:

MegaraFocusTelescope

Recipe:

FocusTelescopeRecipe

Recipe input:

FocusTelescopeRecipeInput

Recipe result:

FocusTelescopeRecipeResult

This observing mode includes the required actions to focus GTC using MEGARA. A bright point source should be identified for this purpose. This mode is an alternative to obtain the best focus of the telescope using the A&G system. Since this mode requires having precise information on the spatial distribution of the flux coming from a point source in a region a few arcsec in diameter the use of the LCB IFU bundle.

Requirements

This mode requires the observation of a bright point source on the sky continuously while the observing mode is being run. Although photometric conditions are not needed the transparency should allow to properly measure the source FWHM on the sky in any exposure of the series. The FOV of the LCB IFU is large enough for these observations to be carried out with one of the sides of the focal-plane cover closed. However, as the default configuration of the instrument with the focal-plane cover in the open position the alignment will be more likely carried out with the cover in that position.

This mode requires having the focal-plane cover configured (at least one of the sides should be open; the most likely configuration will be with the focal-plane cover fully open), the instrument shutter open, to configure the VPH mechanism to select the grating to be used, to set the instrument mode to LCB IFU, to move the focusing mechanism to the position pre-defined for the specific VPH of choice, to expose a certain time and to readout the detector in a series of exposures, being this series the telescope focus image set. A pause in between every exposure in the series should be introduced in order to give time for the M2 to adjust each new focus position in the series and for the M2 control system to inform about its new position, which should then re-start the observing sequence.

Products

The observatory staff should obtain the telescope focus image sets as part of standard preparatory observations (according to GRANTECAN this is usually done every night). Should the focus offset between the ASG and SFS arms (or an imaging instrument in other focus) and that of the MEGARA FC be stable overtime, the use of this mode would be limited to the early stages of characterization of the optimal telescope configuration for MEGARA, or after major changes in the instrument, or if any problem arises. The observatory staff should obtain the telescope focus image sets as part of standard preparatory observations obtained at twilight (although not necessarily every night) or when problems with the telescope focus model are suspected. Also, telescope focus should be revised periodically (e.g. monthly) to correct for potential temperature effects. In general, Auxiliary modes will be typically run once every observing run (e.g. the fine-acquisition ones) or, in the best (most relaxed) case, after a long period of inactivity.

Recipe, inputs and results

class megaradrp.recipes.auxiliary.focustel.FocusTelescopeRecipe(*args, **kwargs)

Process telescope focus images and find best focus.

This recipe process a set of focus images obtained in Focus Telescope mode and returns an estimation of the telescope best focus.

See also

megaradrp.recipes.auxiliary.focusspec.FocusSpectrographRecipe

recipe to measure the focus of the spectrograph

Notes

Images provided in obresult are grouped by the value of their FOCUST keyword. Groups of images are trimmed and corrected from overscan, bad pixel mask (if master_bpm is not None), bias and dark current (if master_dark is not None). Each group is then stacked using the median.

The result of the combination is saved as an intermediate result, named ‘focus2d-#focus.fits’, with #focus being the value of the focus of each group. Apertures are extracted in each combined image, and the resulting RSS file is saved as an intermediate result, named ‘focus1-#focus.fits’.

For each image, the FWHM of the object at position is computed.

Then, the FWHM is fitted to a 2nd degree polynomial, and the focus corresponding to its minimum is obtained and returned in focus_table

class FocusTelescopeRecipeInput(*args, **kwds)

FocusTelescopeRecipeInput documentation.

Attributes:

diffuse_light_imageDiffuseLightCorrection, requirement, optional

Diffuse light correction image

extraction_offsetListOfType, requirement, optional, default=[0.0]

Offset traces for extraction

ignored_sky_bundlesListOfType, requirement, optional

Ignore these sky bundles

master_aperturesMultiType, requirement

Apertures information for extraction

master_biasMasterBias, requirement

Master BIAS image

master_bpmMasterBPM, requirement, optional

Master Bad Pixel Mask

master_darkMasterDark, requirement, optional

Master DARK image

master_fiberflatMasterFiberFlat, requirement

Master fiber flat calibration

master_sensitivityMasterSensitivity, requirement, optional

Master sensitivity for flux calibration

master_slitflatMasterSlitFlat, requirement, optional

Master slit flat calibration

master_twilightMasterTwilightFlat, requirement, optional

Master twlight flat calibration

master_wlcalibWavelengthCalibration, requirement

Wavelength calibration table

methodstr, requirement, optional, default=median

Combination method

method_kwargsdict, requirement, optional

Arguments for combination method

obresultObservationResultType, requirement

Observation Result

positionlist, requirement

Position of the reference object

reference_extinctionReferenceExtinctionTable, requirement, optional

Reference extinction

relative_thresholdfloat, requirement, optional, default=0.3

Threshold for peak detection

sky_rssSkyRSS, requirement, optional

Row Stacked Spectra of the sky

class FocusTelescopeRecipeResult(*args, **kwds)

FocusTelescopeRecipeResult documentation.

Attributes:

focus_tablefloat, product

RecipeInput

alias of FocusTelescopeRecipeInput

RecipeResult

alias of FocusTelescopeRecipeResult

reorder_and_fit(all_images)

Fit all the values of FWHM to a 2nd degree polynomial and return minimum.

run_on_image(img, coors)

Extract spectra, find peaks and compute FWHM.

Spectrograph focus

Mode:

Spectrograph Focus

Usage:

Online

Key:

MegaraFocusSpectrograph

Recipe:

FocusSpectrographRecipe

Recipe input:

FocusSpectrographRecipeInput

Recipe result:

FocusSpectrographRecipeResult

This mode sequence includes the required actions to focus the MEGARA spectrograph. The arc lamps from the ICM will be used for this purpose. MEGARA includes a focusing mechanism at the position of the pseudo-slits. The best image quality for the spectrograph is achieved by using a different focus position for each disperser element (VPH). The focus position is independent of the instrument mode in use (TBC; see next paragraph).

As said above, the two pseudo-slits (LCB and MOS) have to be at the same exact place at the spectrograph entrance to yield the same focus position. If this is not the case MEGARA can correct from this effect by focusing with a fixed offset for all the VPHs. This value has to be added to the nominal focusing position of a VPH with the pseudo-slit used as reference and shall be taken into account in the MEGARA Control System look-up table. Whether these should be one look-up table (i.e. a different focus compromise) for each focal-plane cover configuration is TBD.

Requirements

This mode requires having the focal-plane cover configured (at least one of the sides should be open), the instrument shutter open, to configure the VPH mechanism to select the grating to be used, to set the instrument mode to use, to move the focusing mechanism to the pre-defined focus position for specific VPH of choice, to expose a certain time and to readout the detector in a series of exposures, being this series the spectrograph focus image-sets. The focusing mechanism should be able to change its position in between every two exposures in the series. A pause in between every exposure should be introduced in order to give time for the focusing mechanism to adjust to the new focus position in the series and for the MEGARA control system to inform about its new position, which should then re-start the observing sequence (see below). Whether the focus positions (or range) for each VPH are already pre-defined is TBD.

As part of the on-line quick-look software all images in the series should be pre-processed and several spectra along the pseudo-slit should be extracted and analyzed. This analysis should include the computation of the FWHM of a few unresolved spectra lines at different wavelengths. This software should then decide based on the FWHM values computed at different wavelengths and positions along the pseudo-slit the best focus compromise. The best focus obtained for the VPH of choice should then be stored and used to determine the best foci for all spectral configurations (and instrument modes; TBC).

Procedure

Spectrograph focus image sets through; at least, one of the MEGARA VPHs should be obtained at the beginning of every observing night by either the observer or the staff of the observatory (TBD). Once a VPH is checked, the rest of the values could be corrected relative to this one. It is expected that minor focus corrections should be done as the temperature changes. This could be modeled in further phases and checked at laboratory and/or at the telescope. The observatory staff should obtain an entire sequence of spectrograph focus image sets through all VPHs (and instrument modes; TBC) after major changes in the instrument, long periods of inactivity or when the relative-focus prescriptions (i.e. the spectrograph focus model) are suspected to be inaccurate.

The focus difference (obtained by measuring a particular VPH) will provide the offset focus (due to temperature) and this value will be the same for all VPHs. The Control System will be prepared to update the look-up table with this offset focus value due to temperature.

Products

The best focus, the goodness of the fit of the best focus, a table with the FWHM of the spectral line corresponding to each focus, position along the slit and wavelength, the collapsed PSFs, QA flag, a text log file of the processing and a structured text file containing information about the processing.

Recipe, inputs and results

class megaradrp.recipes.auxiliary.focusspec.FocusSpectrographRecipe(*args, **kwargs)

Process spectrograph focus images and find best focus.

This recipe process a set of focus images obtained in Focus Spectrograph mode and returns different measurements of the spectrograph focus along de detector.

See also

megaradrp.recipes.auxiliary.focustel.FocusTelescopeRecipe

recipe to measure the focus of the telescope

Notes

Images provided in obresult are grouped by the value of their FOCUS keyword. Groups of images are trimmed and corrected from overscan, bad pixel mask (if master_bpm is not None), bias and dark current (if master_dark is not None). Each group is then stacked using the median.

The result of the combination is saved as an intermediate result, named ‘focus2d-#focus.fits’, with #focus being the value of the focus of each group. Apertures are extracted in each combined image, and the resulting RSS file is saved as an intermediate result, named ‘focus1-#focus.fits’.

For each image, peaks are detected every nfibers fibers, and their position, peak flux and FWHM is computed. The image with median focus is taken as reference image, and the peaks of every other image are matched against it.

Then, for each line matched in the series of images, its FWHM is fitted to a 2nd degree polynomial, and the focus corresponding to its minimum is obtained.

The recipe returns:

• focus_table: a table with (x,y,best_focus) for each matched peak,

  with x,y measured in the reference bidimensional image

• focus_wavelength: a structure containing measurements of every

  matched peak in each image

• focus_image: a bidimensional image representing the spatial

  variation of the best focus, using a Voronoi diagram.

class FocusSpectrographRecipeInput(*args, **kwds)

FocusSpectrographRecipeInput documentation.

Attributes:

extraction_offsetListOfType, requirement, optional, default=[0.0]

Offset traces for extraction

master_aperturesMultiType, requirement

Apertures information for extraction

master_biasMasterBias, requirement

Master BIAS image

master_bpmMasterBPM, requirement, optional

Master Bad Pixel Mask

master_darkMasterDark, requirement, optional

Master DARK image

master_wlcalibWavelengthCalibration, requirement

Wavelength calibration table

nfibersint, requirement, optional, default=10

The results are sampled every nfibers

obresultObservationResultType, requirement

Observation Result

tsigmaint, requirement, optional, default=50

Scale factor for row threshold

class FocusSpectrographRecipeResult(*args, **kwds)

FocusSpectrographRecipeResult documentation.

Attributes:

focus_imageProcessedFrame, product

focus_tableArrayType, product

focus_wavelengthFocusWavelength, product

Fine acquisition with the LCB IFU

Mode:

LCB Acquisition

Usage:

Online

Key:

MegaraLcbAcquisition

Recipe:

AcquireLCBRecipe

Recipe input:

RecipeInput

Recipe result:

RecipeResult

This mode sequence includes the required actions to acquire a target with known celestial coordinates and place it at a reference position inside the LCB IFU instrument mode. The reference position for each mode is defined as the center of the fibers (or its associated microlens) that is closest to the bundle footprint geometrical center. In the case of the LCB the reference position will depend on the focal-plane cover configuration. This mode is a refinement of acquisition performed by the telescope or A&G systems.

Requirements

This mode requires having the focal-plane cover configured, the instrument shutter open, to configure the VPH mechanism to select the grating to be used, to set the instrument mode to LCB, to move the focusing mechanism to the position pre-defined for the specific VPH of choice, and to expose a certain time and to readout the detector in a series of exposures, being this series the fine acquisition image set.

As part of the MEGARA on-line quick-look software the image (or images) obtained as part of this observing mode should be processed and the spectra extracted so to determine the position of the centroid of the target in the corresponding field of view. A view of the field should be also produced in order to evaluate whether or not the angle of the Folded-Cass rotator matches that specified by the observer.

Products

Fine acquisition image sets should be obtained at the beginning of the observing night by either the observer or the staff of the observatory (TBD) or every time a problem with the telescope absolute pointing is suspected. Such image sets should be also obtained when an absolute positioning precision of the order of a fraction of the spaxel size is required, better than 0.62 arcsec in this case for the LCB.

The observatory staff should decide whether or not the corrections derived must be applied to the acquisition of other targets during the same observing night or exclusively to the target currently being observed.

Recipe, inputs and results

class megaradrp.recipes.auxiliary.acquisitionlcb.AcquireLCBRecipe(*args, **kwargs)

Process Acquisition LCB images.

This recipe processes a set of acquisition images obtained in LCB Acquisition mode and returns the offset and rotation required to center the fiduciary object in its reference positions.

See also

megaradrp.recipes.auxiliary.acquisitionmos.AcquireMOSRecipe

Notes

Images provided by obresult are trimmed and corrected from overscan, bad pixel mask (if master_bpm is not None), bias, dark current (if master_dark is not None) and slit-flat (if master_slitflat is not None).

Images thus corrected are the stacked using the median. The result of the combination is saved as an intermediate result, named ‘reduced_image.fits’. This combined image is also returned in the field reduced_image of the recipe result.

The apertures in the 2D image are extracted, using the information in master_apertures and resampled according to the wavelength calibration in master_wlcalib. Then is divided by the master_fiberflat. The resulting RSS is saved as an intermediate result named ‘reduced_rss.fits’. This RSS is also returned in the field reduced_rss of the recipe result.

The sky is subtracted by combining the the fibers marked as SKY in the fibers configuration. The RSS with sky subtracted is returned ini the field final_rss of the recipe result.

Then, the centroid of the fiduciary object nearest to the center of the field is computed. The offset needed to center the fiduciary object in the center of the LCB is returned.

class AcquireLCBRecipeInput(*args, **kwds)

AcquireLCBRecipeInput documentation.

Attributes:

diffuse_light_imageDiffuseLightCorrection, requirement, optional

Diffuse light correction image

extraction_offsetListOfType, requirement, optional, default=[0.0]

Offset traces for extraction

extraction_regionListOfType, requirement, optional, default=[1000, 3000]

Region used to compute a mean flux

ignored_sky_bundlesListOfType, requirement, optional

Ignore these sky bundles

master_aperturesMultiType, requirement

Apertures information for extraction

master_biasMasterBias, requirement

Master BIAS image

master_bpmMasterBPM, requirement, optional

Master Bad Pixel Mask

master_darkMasterDark, requirement, optional

Master DARK image

master_fiberflatMasterFiberFlat, requirement

Master fiber flat calibration

master_sensitivityMasterSensitivity, requirement, optional

Master sensitivity for flux calibration

master_slitflatMasterSlitFlat, requirement, optional

Master slit flat calibration

master_twilightMasterTwilightFlat, requirement, optional

Master twlight flat calibration

master_wlcalibWavelengthCalibration, requirement

Wavelength calibration table

methodstr, requirement, optional, default=median

Combination method

method_kwargsdict, requirement, optional

Arguments for combination method

nringsint, requirement, optional, default=3

Number of rings to extract the star

obresultObservationResultType, requirement

Observation Result

pointsListOfType, requirement, optional, default=[(0, 0)]

Coordinates

reference_extinctionReferenceExtinctionTable, requirement, optional

Reference extinction

relative_thresholdfloat, requirement, optional, default=0.3

Threshold for peak detection

sky_rssSkyRSS, requirement, optional

Row Stacked Spectra of the sky

class AcquireLCBRecipeResult(*args, **kwds)

AcquireLCBRecipeResult documentation.

Attributes:

final_rssProcessedRSS, product

offsetlist, product

reduced_imageProcessedImage, product

reduced_rssProcessedRSS, product

rotangfloat, product

RecipeInput

alias of AcquireLCBRecipeInput

RecipeResult

alias of AcquireLCBRecipeResult

Fine acquisition with the Fiber MOS

Mode:

MOS Acquisition

Usage:

Online

Key:

MegaraLcbAcquisition

Recipe:

AcquireMOSRecipe

Recipe input:

RecipeInput

Recipe result:

RecipeResult

The sequence for this observing mode includes the required actions to acquire a list of targets with known celestial coordinates and place each target at the center of a different robotic positioner. The information on the assignment of targets and positioners is included in the form of a set of input catalogues generated off-line by the MEGARA Observing Preparation Software Suite (MOPSS). The reference position for each positioner is the center of the central fiber of the 7-fiber minibundle. This mode is a refinement of the acquisition performed by the telescope or A&G systems.

Requirements

This mode requires having the focal-plane cover configured, the instrument shutter open, to configure the VPH mechanism to select the grating to be used, to set the instrument mode to Fiber MOS, to move the focusing mechanism to the position pre-defined for the specific VPH of choice, to move all robotic positioners with a target associated in the input catalogues to the position of the corresponding target and to expose a certain time and to readout the detector in a series of exposures, being this series the Fiber-MOS fine acquisition image set.

As part of the MEGARA on-line quick-look software, the image (or images) obtained should be processed and the spectra extracted so to determine the position of the centroid of a number of reference targets included in the corresponding field of view and identified as such in the set of input catalogues used for this observing mode. A minimum of three reference sources should be included in each Fiber MOS configuration block in order for this observing mode to generate a solution. The quick-look software should compare the expected and the actual positions of these reference sources in order to determine the best-fitting set of offsets (both in X and Y) and rotation angle to apply to the telescope and Folded-Cass rotator, respectively, to then continue with one of the scientific observing modes described in next Section.

Products

Fine acquisition image sets should be obtained by the observer at the beginning of the observation of each field with the Fiber MOS. The observatory staff should decide whether or not the corrections derived (telescope offset and Folded-Cass rotator angle) must be applied to the acquisition of other fields with the Fiber MOS during the same observing night or exclusively to the target currently being observed.

Recipe, inputs and results

class megaradrp.recipes.auxiliary.acquisitionmos.AcquireMOSRecipe(*args, **kwargs)

Process Acquisition MOS images.

This recipe processes a set of acquisition images obtained in MOS Acquisition mode and returns the offset and rotation required to center the fiducial objects in their reference positions.

See also

megaradrp.recipes.auxiliary.acquisitionlcb.AcquireLCBRecipe

numina.array.offrot

Kabsch algorithm for offset and rotation

Notes

Images provided by obresult are trimmed and corrected from overscan, bad pixel mask (if master_bpm is not None), bias, dark current (if master_dark is not None) and slit-flat (if master_slitflat is not None).

Images thus corrected are the stacked using the median. The result of the combination is saved as an intermediate result, named ‘reduced_image.fits’. This combined image is also returned in the field reduced_image of the recipe result.

The apertures in the 2D image are extracted, using the information in master_apertures and resampled according to the wavelength calibration in master_wlcalib. Then is divided by the master_fiberflat. The resulting RSS is saved as an intermediate result named ‘reduced_rss.fits’. This RSS is also returned in the field reduced_rss of the recipe result.

The sky is subtracted by combining the the fibers marked as SKY in the fibers configuration. The RSS with sky subtracted is returned ini the field final_rss of the recipe result.

Then, the centroid of each fiducial object, marked as REFERENCE in the fibers configuration, is computed. The offset and rotation needed to center each fiducial object in its bundle is computed and returned

class AcquireMOSRecipeInput(*args, **kwds)

AcquireMOSRecipeInput documentation.

Attributes:

diffuse_light_imageDiffuseLightCorrection, requirement, optional

Diffuse light correction image

extraction_offsetListOfType, requirement, optional, default=[0.0]

Offset traces for extraction

extraction_regionListOfType, requirement, optional, default=[1000, 3000]

Region used to compute a mean flux

ignored_sky_bundlesListOfType, requirement, optional

Ignore these sky bundles

master_aperturesMultiType, requirement

Apertures information for extraction

master_biasMasterBias, requirement

Master BIAS image

master_bpmMasterBPM, requirement, optional

Master Bad Pixel Mask

master_darkMasterDark, requirement, optional

Master DARK image

master_fiberflatMasterFiberFlat, requirement

Master fiber flat calibration

master_sensitivityMasterSensitivity, requirement, optional

Master sensitivity for flux calibration

master_slitflatMasterSlitFlat, requirement, optional

Master slit flat calibration

master_twilightMasterTwilightFlat, requirement, optional

Master twlight flat calibration

master_wlcalibWavelengthCalibration, requirement

Wavelength calibration table

methodstr, requirement, optional, default=median

Combination method

method_kwargsdict, requirement, optional

Arguments for combination method

obresultObservationResultType, requirement

Observation Result

reference_extinctionReferenceExtinctionTable, requirement, optional

Reference extinction

relative_thresholdfloat, requirement, optional, default=0.3

Threshold for peak detection

sky_rssSkyRSS, requirement, optional

Row Stacked Spectra of the sky

class AcquireMOSRecipeResult(*args, **kwds)

AcquireMOSRecipeResult documentation.

Attributes:

final_rssProcessedRSS, product

offsetlist, product

reduced_imageProcessedFrame, product

reduced_rssProcessedRSS, product

rotangfloat, product

RecipeInput

alias of AcquireMOSRecipeInput

RecipeResult

alias of AcquireMOSRecipeResult